Starke Sound Fiera4 4CH Amplifier Does It Meet Power Spec?

[PENG]

are we all explaining the same phenomena but disagreeing with exactly how to characterize what is going on? It seems my explanation wasn’t so off from what Bruno said, but I see it also matching what you said.

what am I missing.

Gene beat me to it. Yes we are all on the same page. Ic6 somehow missed your key words, i.e. "half", "share". Though as I commented on this also, the way you tried to explain it could be confusing or misleading, and now we can see at least one person did get confused. Bruno's words as quoted by you, are clearer, though his first paragraph is much preferred (just my opinion as an EE), and his second paragraph, while also clear, seemed overkilling it, therefor against the K-I-S-S principle.

Again, there is nothing wrong with the way you put it, but it could have been kept simpler and clearer such as Ic6's though I agreed with paulgyro's post about his tone, that is uncalled for.

 

[gene]

Of course there are practical limits to a BTL implementation. But this discussion was about theory, in the context of the reviewer's statement that "with a BTL or bridge tied load, you double the voltage differential because the amplifier is run in differential mode. This doubles the power as each half of the amplifier is also now seeing half the impedance." If the statement was something like "this doubles the power supplied by each half of the amplifier (i.e. quadruples the power of the entire amplifier) as each half of the amplifier is also now seeing half the impedance" that would be acceptable, provided a further explanation of the "virtual ground" in the center of the shared load, similar to the one Bruno offered. But, as written, the statement suggested the overall BTL power only doubles (also consistently with practical observations), which is simply not true absent limitations, e.g. for relatively small output levels.

> since we have two voltage sources in series, isn’t this the same as saying each sees half the load?

In a BTL, you do not have two voltage sources in series, you have them at the opposite sides of the shared load. Two voltage sources in series would imply they are directly connected to each other. In that scenario, if one source produced voltage V1 and the other voltage V2, together they would produce voltage V1+V2 and each would see the full (not half of) load because a voltage source has, by definition, zero impedance.

Alright, enough of this already, we beat this horse to death.

Now, since we have @gene 's attention, where is the follow-up to the Yamaha RX-A6A bench test you did last December?
"I will be conducting critical listening tests in the formal review process coming next." Can't find one.

Nobody ever claims 2 voltage sources were in series. It's a push/pull scenario with the load in series between the two voltage sources. There are BTLs and parallel amp options which allows for doubling the current. I believe some Class D modules allow the designer to implement both BTL and parallel connections for increased current.

I am behind on most of my reviews and still need to get to the RX-A6A one. I can say that with just 2CH stereo, the amp section is phenomenal. I think it sounds every bit as good as my Denon A110 integrated amp. It's really that good.

 

[lc6]

Nobody ever claims 2 voltage sources were in series. It's a push/pull scenario with the load in series between the two voltage sources. There are BTLs and parallel amp options which allows for doubling the current. I believe some Class D modules allow the designer to implement both BTL and parallel connections for increased current.

I am behind on most of my reviews and still need to get to the RX-A6A one. I can say that with just 2CH stereo, the amp section is phenomenal. I think it sounds every bit as good as my Denon A110 integrated amp. It's really that good.

@Matthew J Poes wrote: "since we have two voltage sources in series..."
@gene wrote: "Nobody ever claims 2 voltage sources were in series..."
@lc6 : I think you guys need to get your story straight. Until then, further discussion of this is rather pointless.

@Matthew J Poes indicated that in the Starke design, there are two chips per channel, as opposed to one chip in competing implementations. But is it truly the case? In the TPA3255 application note (see p. 28), there is a mono PBTL configuration, in which two BTL amps (both part of the same chip) together drive a single load. As I mentioned before, connecting amps from different chips in parallel without load-balancing resistors (which would increase output impedance) would be problematic because it would be difficult to guarantee an even current spread. So perhaps PBTL is actually used?

Good to know that RX-A6A sounds really good.

 

[buckchester]

Nobody ever claims 2 voltage sources were in series. It's a push/pull scenario with the load in series between the two voltage sources. There are BTLs and parallel amp options which allows for doubling the current. I believe some Class D modules allow the designer to implement both BTL and parallel connections for increased current.

I am behind on most of my reviews and still need to get to the RX-A6A one. I can say that with just 2CH stereo, the amp section is phenomenal. I think it sounds every bit as good as my Denon A110 integrated amp. It's really that good.

Gene, I think recall you saying you were going to conduct a side by side listening test between the Salon 2 and 328be? Do you still plan to do this? I would be very interested in hearing your results.

 

[gene]

Gene, I think recall you saying you were going to conduct a side by side listening test between the Salon 2 and 328be? Do you still plan to do this? I would be very interested in hearing your results.

Impossible since I don't have access to Salon 2s. I know for a fact the Salon2 have superior bass extension and output though. The F328Be are a bit weak in bass for a speaker of that size and price.

 

[buckchester]

Impossible since I don't have access to Salon 2s. I know for a fact the Salon2 have superior bass extension and output though. The F328Be are a bit weak in bass for a speaker of that size and price.

Yes I was aware the Salon2 had deeper bass. But I thought they designed the 328 to have weaker bass so that it could play louder with less distortion above the deep bass? Pair either with a pair of really good subs, and which do you think would sound better?

 

[gene]

Yes I was aware the Salon2 had deeper bass. But I thought they designed the 328 to have weaker bass so that it could play louder with less distortion above the deep bass? Pair either with a pair of really good subs, and which do you think would sound better?

Yea it was designed for higher sensitivity and it plays really loud and clean.xmated with good dual subs. The F328be will have the advantage. As standalone 2CH, no subs, Salon2 for the win.

 

[Golfx]

@Matthew J Poes wrote: "since we have two voltage sources in series..."
@gene wrote: "Nobody ever claims 2 voltage sources were in series..."
@lc6 : I think you guys need to get your story straight. Until then, further discussion of this is rather pointless.

@Matthew J Poes indicated that in the Starke design, there are two chips per channel, as opposed to one chip in competing implementations. But is it truly the case? In the TPA3255 application note (see p. 28), there is a mono PBTL configuration, in which two BTL amps (both part of the same chip) together drive a single load. As I mentioned before, connecting amps from different chips in parallel without load-balancing resistors (which would increase output impedance) would be problematic because it would be difficult to guarantee an even current spread. So perhaps PBTL is actually used?

Good to know that RX-A6A sounds really good.

As I read through your postings I tried to find value in them. I didn’t see any. What you added was disapproval and in so doing recruited it for yourself.

 

[nexus99]

It looks like the summary for the thread is that the new Fiera4 is a fine piece of gear and the numbers written on the website meet the measured output. As measured by several different groups. And the ASR folks really hate this and still want to take pot shots. Because... well, who knows why right? And its on a killer sale now and that makes them even more angry... You can't make this stuff up!

 

[dlaloum]

I have looked to see what the damping factor of these class D amps actually is. For other members damping factor is the load impedance (speaker impedance) divided by the amplifier source impedance. So for example my Quad 909 amps have a source impedance of 0.05 ohms. So driving an 8 ohm load that gives a damping factor of 20, which for a Class AB amp is considered very good.

If we look a what has been measured for class D amps they stack up well.

This is the Hypex N-core.

This is the damping factor for the Fiera4

You can see that their is significant drop starting above 2000 Hz, and by 20K it is poor. Again this is with an 8 ohm load. With a four ohm load the damping factor will be halved.

On that parameter the Hypex shows excellent performance. The Fiera4 I think might well not be a stellar performer with four ohm speakers presenting complex loads above 5K.

So on that parameter the Hypex scores higher. It is not clear to me why the source impedance appears to be rising with frequency in the Fiera4. As of yet I have no experience with class D amps. I am not aware of class A or AB amps, having a frequency dependent source impedance. Although the Quad performs as class A, the output transistors are biased class B, and a small class A amp provides a feed forward error correction, resulting in spec. that is like a class A amp, but without the inefficiency of class A biasing. That is unique to Quad current dumping amps.

I too am a long time fan of the Quad amps, I have two 606's currently sitting idle however, due to insufficient current capacity for optimal performance with my 'current' speakers...

Having said that - there are a number of designs that seem to have used similar principles to the Quad amps (with a secondary "current dumper" following a primary high quality voltage amp).

Various "transimpedance" and "feedforward" designs seem to use similar concepts - and often the related patents refer to Walkers Current Dumping patents.

Threshold and Nakamichi Stasis amps, the current Benchmark AHB2, and the Devialet amp (which uses a Class D follower to provide the heavy lifting rather than a class B stage) - I have a feeling in the back of my mind that some of the Sansui's might have done something similar too back in the 80's.

What I find interesting though - is that all these other designs end up with highly complex designs, for minimal aditional gain, over the relatively simple Peter Walker designs with few parts.... The Quad amps are easily maintained, provide high performance, can be refurbished economically... their only weakness is something I discovered only once I had a very demanding low impedance speaker... where the current available from the 606's was a bit marginal at 2 ohm... they still sound good with these speakers... but something with much more current just sounds that little bit better.

As you say, it's the difficult speakers that wean the wheat from the chaff.... I should investigate the more recent Quad amps to see whether there is one that can provide more current.... @ 2 ohm

 

[PENG]

I too am a long time fan of the Quad amps, I have two 606's currently sitting idle however, due to insufficient current capacity for optimal performance with my 'current' speakers...

Having said that - there are a number of designs that seem to have used similar principles to the Quad amps (with a secondary "current dumper" following a primary high quality voltage amp).

Various "transimpedance" and "feedforward" designs seem to use similar concepts - and often the related patents refer to Walkers Current Dumping patents.

Threshold and Nakamichi Stasis amps, the current Benchmark AHB2, and the Devialet amp (which uses a Class D follower to provide the heavy lifting rather than a class B stage) - I have a feeling in the back of my mind that some of the Sansui's might have done something similar too back in the 80's.

What I find interesting though - is that all these other designs end up with highly complex designs, for minimal aditional gain, over the relatively simple Peter Walker designs with few parts.... The Quad amps are easily maintained, provide high performance, can be refurbished economically... their only weakness is something I discovered only once I had a very demanding low impedance speaker... where the current available from the 606's was a bit marginal at 2 ohm... they still sound good with these speakers... but something with much more current just sounds that little bit better.

As you say, it's the difficult speakers that wean the wheat from the chaff.... I should investigate the more recent Quad amps to see whether there is one that can provide more current.... @ 2 ohm

For it's rated output 140 W into 8 ohms, that's about the same as any flagship D, M or Y AVRs but if you look at the specs you can see that the Quad 606 has excellent current capability. That doesn't mean it is suitable for 2 ohm loads, it may be fine but as always it would depend on your listening habits, distance and the specific speakers.

Is your current speaker's impedance 2 ohms nominal, or 2 ohms minimum?

Everything is relative, the 606's specified "maximum" current is 12 A, one channel, that would be 12^2*2 = 288 W into 2 ohm. Obviously it can't handle a 2 ohm load at that level, but for transient peaks in music, if the power requirement is, say, less than 140 W at your maximum listening level then it should have enough current.

Any load below 4 ohm nominal is going to be tough on power amps regardless of the brands. Then again it all depend on the factors I mentioned, so when shopping for one you need to read the detailed specs and measurements if available carefully and do your math too because purchase.

 

[PENG]

As I read through your postings I tried to find value in them. I didn’t see any. What you added was disapproval and in so doing recruited it for yourself.

His technical points are valid, and informative but too bad he wrote it the way he did..

 

[lc6]

His technical points are valid, and informative but too bad he wrote it the way he did..

Yes, comrades, going forward I will fall in line and my posts will be full of approval, likes and general admiration for everything that is written on here. This way, I will only get approval from everyone myself. Could you please point me to a little AH red (or perhaps green?) book, from which I could get guidance on how to improve my behavior?

 

[Trell]

Yes, comrades, going forward I will fall in line and my posts will be full of approval, likes and general admiration for everything that is written on here. This way, I will only get approval from everyone myself. Could you please point me to a little AH red (or perhaps green?) book, from which I could get guidance on how to improve my behavior?

You don’t understand why the following by you is obnoxious? This is not popular on ASR either.

>>>Buddy, I do not know which EE school you went to (if at all) and what kind of reading comprehension problems you have (I did not claim you said an SE amp sees half the load, I quoted you saying a BTL amp does). But let me try to explain a bridged amp circuit to you as simply as I can.<<<

 

[lc6]

You don’t understand why the following by you is obnoxious? This is not popular on ASR either.

>>>Buddy, I do not know which EE school you went to (if at all) and what kind of reading comprehension problems you have (I did not claim you said an SE amp sees half the load, I quoted you saying a BTL amp does). But let me try to explain a bridged amp circuit to you as simply as I can.<<<

The reason for that forceful response should have been obvious by now. The reviewer endlessly argued with me, conveniently ignoring some points while reiterating technical nonsense without any good explanation, demonstrating lack of basic knowledge of circuitry he was evaluating (which he only later admitted) and also accusing me of misrepresentation. At some point, an end had to put to all that back-and-forth, and that is what it took.

Then Gene got into the middle of the discussion, bringing up all sorts of crap about Amir, ASR and its members, trying to drag Erin of EAC into this, all for no good reason. He subsequently initiated a side discussion and we exchanged our points of view. I do not know all the history between them, but I'd rather see competent and informative reviews than dart throwing from both sides.

 

[gene]

Yes, comrades, going forward I will fall in line and my posts will be full of approval, likes and general admiration for everything that is written on here. This way, I will only get approval from everyone myself. Could you please point me to a little AH red (or perhaps green?) book, from which I could get guidance on how to improve my behavior?

You can take a couple of days off to self reflect now.

 

[ryanosaur]

The thing most disappointing is the fact people who disagree can't keep it civil. It's not difficult to have polite discourse even in the face of disagreement.

 

[Matthew J Poes]

I absolutely made some mistakes In my description here but a lot of the disagreements were pedantic. Some of what I wrote that was wrong was simply a typo caused by the fact that I typed it on my phone with two kids running around and dinner cooking. For those that don’t know, My wife works evenings so I am responsible for dinner and watching the kids after 5pm. It’s hard for me to have deep technical conversations on forums with that going on. I suppose next time I should formulate my responses more cautiously.

to correct one of the pedantic issues being discussed. I didn’t mean to say it has two chips. I meant channels. Each actual channel is the amp uses two channels of the chip in a BTL arrangement. When it’s bridged, it uses all four channels in a PBTL arrangement.

the Ti module can be configured for four SE amps, two SE and one BTL, two BTL, or one PBTL. A number of the inexpensive versions on Amazon were wired as a 2.1 amp. So not really comparable. A few do use the same BTL arrangement and so in theory could be as powerful as this. But they appear to use much weaker power supplies and lower rail voltages. So they don’t put out as much power. I am sure there is going to be some exception. But I also don’t think we can condemn a product because there happens to be some cheaper similar alternatives. That will always be true.

As for the brand. I know that many people were really put off by how Starke handled the prior situation. None of us at Audioholics feel it was handled well. A lot of things said should not have been and clearly the old amplifier was wildly mis-specified. I can’t say way. I really don’t know where those numbers came from. Many of you know Dan Wiggins. He has never struck me as a liar or grifter. He’s a talented engineer that brought us a ton of really great products and technologies. Something clearly went wrong in bringing the last product and it’s marketing to the public. I want to believe it was an inadvertent mistake that was then mishandled when it came to light. But in talking to Scott about this amplifier and about the situation, it seems like they recognized that prior amp was a problem and were seeking to restore faith with a better product and more accurate specs. I reviewed the product and not the brand. I really can’t be asked to justify what they say or do. The amp seems fine for what it is, with respectable performance.

I can also say this. Purely because I am busy and lack enough time to stay on top Of my reviews, everything I review typically gets used for a long time. Meaning I likely do a better job than most at testing reliability. I even delay some reviews when j detect potential reliability problems that I want to work out before giving my review. This amp was tested about 2 months ago and has been in use in various forms since then. I was too lazy to connect the trigger so it’s running 24/7. I can’t test it for years obviously but months is still better than days.

 

[Matthew J Poes]

Gene beat me to it. Yes we are all on the same page. Ic6 somehow missed your key words, i.e. "half", "share". Though as I commented on this also, the way you tried to explain it could be confusing or misleading, and now we can see at least one person did get confused. Bruno's words as quoted by you, are clearer, though his first paragraph is much preferred (just my opinion as an EE), and his second paragraph, while also clear, seemed overkilling it, therefor against the K-I-S-S principle.

Again, there is nothing wrong with the way you put it, but it could have been kept simpler and clearer such as Ic6's though I agreed with paulgyro's post about his tone, that is uncalled for.

Thank you and much appreciated. I am
Always happy to learn. Tone certainly helps to avoid defensiveness.

 

[Trebdp83]

Never make excuses, only corrections when necessary. Mistakes can be made and then corrected easily enough.